Tomography

Tomography

Acquisition of images with the specimen tilted at multiple angles over a wide angular range (e.g. -70° to +70°), followed by tomographic reconstruction using back-projection methods, generates three-dimensional rendering of the imaged object. The tomographic rendering allows three dimensional analyis of object shape and morphology, and analysis of, for instance, the distribution of nanostructures and nanoparticles (e.g. of nanometric objects such as nanotubes, atmospheric particles, catalysts supports and catalyst particles). The technique requires specimen holders which have a high angular range, and microscope pole pieces that can accommodate the high tilt angles. Typically the images must be free from coherently-scattered (e.g. elastically-scattered) electrons; therefore Z-contrast imaging in STEM is normally used.